Throughout my scientific career I have been involved in the study of host-pathogen interactions, with an emphasis on bioengineering, microbiology, immunology, and vaccine development. Training in virology, molecular biology, and computational methods has helped me answer a wide variety of scientific questions. The project proposed here is designed to bridge my transition from a postdoctoral fellow to an independent investigator in an academic setting to continue my pursuit of using creative approaches to high-impact, adventurous research to understand the host response to pathogenic infection. Research: Innate immunity refers to the body's initial response to curb infection upon exposure to invading organisms. While the detection of pathogen-associated molecules is an ancient form of host defense, if dysfunctional, it can cause autoimmune disease, which affects over 20 million Americans. The innate immune response is the first line of defense to microbial infection, and it is initiated through the activation of receptors recognizing conserved molecules that are signature of pathogenic infection. Recently, STING (STimulator of INterferon Genes), an intracellular sensor of cytosolic DNA was discovered. STING is critical to the innate immune response during viral and bacterial infection, yet animals exhibiting STING hyperactivation at birth display inflammatory autoimmune disease. While the downstream signaling events occurring after STING activation are well understood, little is known about the mechanisms responsible for STING activation. To address this question, I propose an orthogonal approach utilizing Drosophila melanogaster to investigate STING function and the molecules that stimulate it. This approach will complement the ongoing studies of STING in a mammalian system. In Aim 1, we will determine how human STING and Drosophila STING (dSTING) are similar, providing evidence that dSTING is the bone fide ancestor of human STING. We will assess the capacity of dSTING to bind nucleic acids and characterize the domains of dSTING to determine which are critical for nucleic acid binding and intracellular localization. In Aim 2, we will create a dSTING knockout fly to study the role of dSTING in the innate immune response to infection. Gene expression analyses will be used to functionally determine how the loss of dSTING contributes to an impaired innate immune response, as compared to that of a genomic rescue fly. Aim 3 will utilize next-generation sequencing to identify the nucleic acids that bind t dSTING during microbial infection, providing insight to the specificity of the ligand for STING, a site for potential therapeutic intervention. Together, these studies using the genetically malleable Drosophila model system will improve our understanding of STING function through the extrapolation of the results into the mammalian system for further experimentation. The information gained in this study will have broad-ranging impacts in innate and autoimmunity towards to the development of therapeutics to treat microbial infection and autoimmune disorders. Environment: This project complements the ongoing research on innate immunity of my proposed mentor, Dr. Glen Barber. The work will also setup new collaborations with my co-mentor, Dr. Grace Zhai. Both mentors will provide invaluable mentorship throughout the K99 phase of the award, giving me the training necessary for the rise to independence. The University of Miami has superb facilities, equipment, and outstanding faculty who study microbiology and immunology, through the use of exciting techniques and animal models.